This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A005631 M1628 #22 Jul 23 2022 19:26:30
%S A005631 1,2,6,18,60,200,760,2888,11856,48672,215904,957728,4506304,21203072,
%T A005631 105494400,524880000,2737670400,14279148032,77836363264,424289980928,
%U A005631 2405307227136,13635728197632,80188215392256,471566299547648,2867649768509440,17438513317683200
%N A005631 Bishops on a 2n+1 X 2n+1 board (see Robinson paper for details).
%D A005631 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A005631 R. W. Robinson, <a href="http://dx.doi.org/10.1007/BFb0097382">Counting arrangements of bishops</a>, pp. 198-214 of Combinatorial Mathematics IV (Adelaide 1975), Lect. Notes Math., 560 (1976). [The sequence psi(2k+1).]
%H A005631 R. W. Robinson, <a href="/A000899/a000899_1.pdf">Counting arrangements of bishops</a>, pp. 198-214 of Combinatorial Mathematics IV (Adelaide 1975), Lect. Notes Math., 560 (1976). (Annotated scanned copy)
%p A005631 For Maple program see A005635.
%t A005631 B[n_] := B[n] = Which[n == 0 || n == -2, 1, OddQ[n], B[n - 1], True, 2*B[n - 2] + (n - 2)*B[n - 4]];
%t A005631 a[n_] := B[n + 1]*B[n + 2]/2;
%t A005631 Table[a[n], {n, 0, 25}] (* _Jean-François Alcover_, Jul 23 2022, after Maple code for A123071 *)
%Y A005631 Equals A123071(n)/2, n >= 1.
%Y A005631 Cf. A005635.
%K A005631 nonn
%O A005631 0,2
%A A005631 _N. J. A. Sloane_
%E A005631 More terms from _N. J. A. Sloane_, Sep 28 2006